Method for moving a headrest in the event of a rear-end collision and arrangement of a headrest on a vehicle seat

ABSTRACT

A method for moving a head restraint of a vehicle seat in the event of a rear-end collision and an arrangement of a head restraint on a vehicle seat are provided. In the event of a rear-end collision, the head restraint can be moved in the forward direction of travel by a drive device, and an impact device absorbs a rearward movement of an upper body of an occupant located on the vehicle seat.

BACKGROUND OF THE INVENTION

This application claims the priority of 101 42 926.6, filed Sep. 1, 2001, the disclosure of which is expressly incorporated by reference herein.

The present invention relates to a method for moving a head restraint of a vehicle seat in the event of a rear-end collision, and to an arrangement of a head restraint on a vehicle seat, which arrangement is provided in particular for carrying out this method.

Investigations have revealed that, in particular in the event of rear-end collisions, serious injuries to the cervical spine occur in large numbers. Such injuries to the cervical spine have proven problematic, in particular because the healing process is often very drawn out and is associated with high healing costs and corresponding demands made of insurance companies.

It is, therefore, a great matter of concern for the vehicle industry to provide devices for protecting occupants in vehicles, in which the devices reduce or even prevent injuries to the cervical spine, particularly in the event of rear impact collisions, in which whiplash trauma occurs even at low impact speeds of between approximately 10 km/h and 40 km/h.

In the opinion of medical experts, injuries to the cervical spine and the known whiplash trauma due to a movement of the head relative to the upper body occur if the head is moved relative to the upper body in the rearward direction of travel. In addition, injuries to the cervical spine are also incurred due to the neck muscles being over-rotated after what may be referred to as a “rebound”.

On account of these findings, devices for reducing or avoiding injuries to the cervical spine in a “rear-end crash” aim to support the head and the back of a vehicle occupant in such a manner that, in the event of a crash, there is no relative movement of the head toward the upper body and a movement of the upper body in the forward direction of travel is suppressed as far as possible.

To date, the prior art has disclosed a number of different systems in order to reduce or even avoid injuries to the cervical spine. Thus, for example, DE 197 43 339 A1 discloses a seat and head restraint arrangement having a seat backrest frame with an upper and a lower part. The upper part of the seat backrest frame has a transverse frame element and the lower part has at least one lower section comprising a pair of spaced apart side elements. Furthermore, this arrangement has a head restraint which is fitted to the transverse frame element, an impact mechanism which is positioned between the side elements of the lower part and is fastened to the upper part, and a rotary joint which connects the upper and the lower part and defines an axis of rotation. The upper part and the head restraint can be pivoted about this axis of rotation forward from a normal position and can thereby pivot the impact mechanism to the rear from a normal position. Furthermore, a spring pretensions the upper part, the head restraint and the impact mechanism into their normal position.

If, in the case of an arrangement of this known type, the rear of the vehicle is exposed to an impact, most of the upper body of the occupant has a tendency to move in a relative manner to the rear while the shoulders and the head have a tendency to move in the forward direction of travel. In this known arrangement, the body acts on an impact plate which pivots out to the rear. This pivoting movement has the effect of moving the upper part of the seat backrest frame and the head restraint forward about the axis of rotation toward the occupant's shoulders and head. Therefore, when the occupant moves rearward, the upper part of the seat backrest frame and the head restraint are moved forward thereby counteracting injuries to the cervical spine in the event of a rear-end crash.

In the case of this system which is activated by the relative rearward movement of the occupant, it has proven disadvantageous that the triggering of the system is dependent solely on the weight and the position of the occupant. For this reason, it is always necessary in such a system for it to be matched to the particular occupant. A further disadvantage of this solution is that the movement of the occupant cannot be sufficiently counteracted in the case of a minor rear-end crash.

In addition, the prior art also discloses what are referred to as active systems, in which an active head restraint can be designed such that an airbag is contained in the head restraint. Depending on the outlay on sensors, the activation of a system having an airbag can take place taking account of the weight and the position of the vehicle occupant or irrespective thereof. However, in order to ensure that the airbag is triggered even in relatively minor accidents, low triggering thresholds are frequently set, so that the airbag is always completely deployed even in minor rear-end collisions.

This means that the occupant's forward movement, which is actively triggered by the airbag, is always of the same magnitude no matter how severe the rear-end collision actually is. There is thus no differentiation between relatively minor and more severe accidents, so that, under some circumstances, the active system always causes a sharp forward movement of the head region of the vehicle seat which may result in the occupant being injured in the event of only a minor rear-end collision.

SUMMARY OF THE INVENTION

Starting from this prior art, the invention is based on the An object of the present invention is to provide a method for moving a head restraint in the event of a rear-end collision and an arrangement of a head restraint on a vehicle seat, with which the injuries in the region of the cervical spine in the event of a rear-end crash can be reduced even further without unnecessarily harming the occupant.

This object is achieved by a method first using at least one driving device to effect the movement and assisting the movement by vehicle occupant's upper body located on the vehicle seat and by an arrangement of a head restraint in a rear-end collision, the head restraint is movable in the forward direction of travel by the at least one drive device and an impact device which absorbs a rearward movement of the vehicle occupant's upper body located on the vehicle seat.

In the case of the method and the arrangement of a head restraint on a vehicle seat according to the invention, the combination of the movement of the head restraint in the event of a rear-end collision in the forward direction of travel by way of a drive device and this movement being assisted by a movement of an upper body of an occupant located on the vehicle seat being transmitted has proven very advantageous. A system operating in such a manner, in which preferably first of all the activation by way of the drive device takes place followed by the assistance by the occupant, ensures that the head restraint is displaced in good time and to a sufficient extent in the forward direction of travel both in minor and also in severe rear-end collisions. This provides a system which counteracts injuries to the cervical spine and which can be activated irrespective of the vehicle occupant's weight and position.

The method and the arrangement according to the invention provide the further advantage that, in the event of a rear-end crash, the movement of the head restraint in the forward direction of travel does not take place over a predetermined, maximum path of displacement, but rather is assisted by the relative movement of the upper body of the occupant and therefore takes place in a proportioned manner. Thereby, the movement of the occupant is correspondingly smaller in the event of an only minor rear-end impact and the path of displacement of the head restraint is correspondingly shorter than in the case of a more severe rear-end impact.

Furthermore, the method and arrangement according to the invention are distinguished by the fact that a complex adaptation to a backrest and cushion structure and also stiffness of the vehicle seat is rendered superfluous, and a conflict between designing the vehicle seat and the head restraint in terms of comfort and safety is avoided.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified front view of an arrangement according to the present invention of a head restraint on a vehicle seat in the normal position;

FIG. 2 is a side view of the arrangement of a head restraint on a vehicle seat according to FIG. 1 but without the cushion elements;

FIG. 3 is a front view of the arrangement of a head restraint on a vehicle seat according to FIGS. 1 and 2 during a movement of the head restraint in the forward direction of travel as a consequence of a rear-end collision;

FIG. 4 is a side view of the arrangement according to FIG. 3 without the cushion elements;

FIG. 5 is a perspective front view of an arrangement of a head restraint on a vehicle seat with an alternative drive device to the variant according to FIGS. 1 to 4; and

FIG. 6 is a perspective rear view of the arrangement according to FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference now to the drawing figures, an upper region of a vehicle seat 1 of a motor vehicle is illustrated in part and in simplified form, with a backrest 2 (shown schematically) being connected to a head restraint 3.

The arrangement of the head restraint 3 on the vehicle seat 1 is provided such that, in the event of a rear-end collision, the head restraint 3 is moved in the forward direction of travel by way of a drive device 4 and an impact device 5 which absorbs the movement of an upper body of an occupant located on the vehicle seat 1.

A frame 6 which protrudes with two column-like tubes 7, 8 into the upholstery of the head restraint 3 is provided for holding the head restraint 3. The columns 7, 8 can be vertically adjustable in a conventional manner, thus enabling the height of the head restraint 3 to be matched to the height of the vehicle occupant's head.

In its region facing the backrest 2, the frame 6 forms an approximately U-shaped profile with two limbs, each of which is connected to a spindle drive 9. Each spindle drive 9 has a spindle 10 which can be driven by a motor 11 which is configured here as an electric motor, and by a step-down gear 19.

Alternatively, a drive may also be provided by just one motor which acts on a spindle drive and, via a connecting shaft, also on the second spindle drive. In such a variant, in which just one motor, which can be driven electrically, pneumatically or hydraulically, is required, a greater tolerance in respect of the exact synchronism of the drives of the spindle drives is permissible.

When the spindle drive 9 is actuated, a holder or spindle nut 12 which can be rotated on the spindle 10 and is connected to the frame 6 via two spindle-nut holders 13 is moved axially on the spindle 10. Thus, in the event of a rear-end collision, the spindle 10 is driven by the electric motor 11 so that the spindle nut 12 is moved away from the electric motor 11 in a direction of movement designated by an arrow X in FIG. 4. In this case, the spindle 10 advantageously has a self-locking device.

The frame 6 can be pivoted via an oscillating link 14 about an axis of rotation 15 fixed on the seat back. The pivot axis 15 in the illustrated embodiment runs through two pivots 16, 17 which are arranged symmetrically to each other and in the present case are formed in turn by a screw fastening to a seat back structure (not illustrated in detail). Furthermore, the impact device 5 is connected pivotably via a further oscillating link 18 to the seat back structure by the screw fastenings 16, 17.

The impact device 5 has an impact plate 20 which extends between the U-limbs of the frame 6, in a plane running essentially parallel to the backrest 2, level with the upper body of a vehicle occupant. In the illustrated embodiment, the impact plate 20 is fastened on a frame 21 which has a similar geometry to the frame 6 for holding the head restraint 3. The frame 21 forms an approximately U-shaped profile within the U-profile of the frame 6 and, toward the head restraint 3, has two guide rods 22, 23 which are guided in a guide 24 fixed on the seat back.

The guide 24 which is fixed on the seat back at the same time constitutes a guide sleeve for the columns 7, 8 of the frame 6. The respective passage 25 of the column 7 or 8 through the guide sleeve 24 is designed with a kinematic pivoting point 26 which permits the frame 6 to pivot about the axis of rotation 15.

A strut-like holder 27 is fastened in each case to the U-limbs of the frame 21 of the impact device 5, as an extension of those limbs. The holder 22 is connected fixedly in turn to a securing device 28 for the electric motor 11 of the drive device to create a fixed connection between the impact device 5 and the drive device 4.

In operation of the present arrangement, the head restraint 3 is actuated, in the event of a rear-end collision, from the normal position, which is shown in FIG. 1 and FIG. 2, in such manner that it moves in the forward direction of travel Y, as illustrated in FIG. 3 and FIG. 4.

In the event of a rear-end collision which can be detected by a known sensor mechanism, a suitable controller which may, for example, be already present in the vehicle, is used to activate the drive device 4 by the electric motor 11 thereof driving the spindle drive 9 to move the spindle nut 12 axially to the rear on the spindle drive in the installed position. The frame 6 for holding the head restraint 3 is thereby pivoted by the oscillating link 14 about the axis of rotation 15 and the kinematic pivoting point 26 in the guide sleeve 24, so that the head restraint 3 is displaced in the forward direction of travel Y as seen in FIG. 4. In this case, the displacement of the head restraint 3 takes place irrespective of the weight of the occupant who is to be protected and whose head is moved in a relative manner to the rear in the event of a rear-end collision.

Depending on the path of adjustment on the spindle 10 and the pivoting angle about the axis of rotation 15, provision may be made for the displacement of the head restraint 3 by the drive device 4 to take place irrespective of the severity of the accident so that, even in the event of a very minor accident, a required deflection of the head restraint 3 is always ensured. However, the activation of the drive device 4 may also take place as a function of certain parameters, such as, for example, an occupant's position or a deceleration of the vehicle or further parameters defining the severity of the accident, with the result that the displacement of the head restraint 3 takes place in a proportioned manner.

In the event of a rear-end collision, the upper body of a vehicle occupant is always moved to the rear too, this movement taking place, however, relative to the movement of the head. In the present arrangement, the rearward movement of the upper body is used to assist the forward movement of the head restraint 3.

If, in the event of a rear-end collision, the occupant is pushed with his upper body to the rear into the vehicle seat 1, the occupant presses the impact plate 20 of the impact device 5. The plate 20 is arranged in the seat backrest 2, away to the rear, in which case the impact plate 20 and the frame 21 are likewise pivoted about the axis of rotation 15. Since the drive device 4 which is connected to the frame 6 for holding the head restraint 3 is connected to the impact device 5 via the motor-securing device 27, the drive device 4 is pivoted together with the impact device 5 through a further angle of rotation about the axis of rotation 15 fixed on the seat back. Consequently the head restraint 3 being further displaced in the forward direction of travel Y.

The beginning of the movement of the impact device 5 is illustrated in FIG. 3 and FIG. 4. With this combined system, in which first of all the head-restraint forward movement is activated by the drive device 4, the movement then being assisted by the impact device 5 on account of the movement of the occupant, the activation of the head restraint 3 can be set so that, even with lightweight people and relatively minor rear-end collisions, for example at a differential speed of up to 10 km/h, the drive device 4 causes the head restraint 3 to be deflected in good time and sufficiently for the head of the occupant located on the vehicle seat 1 to come into contact with it while, however, even in the case of a very severe rear-end crash, the head restraint 3 can be sufficiently displaced under assistance by the impact device 5.

The actuation of the drive device 4, which preferably takes place before the actuation of the impact device 5, should take place at such an early point that the problem, as known in the case of airbags, of the head restraint “shooting at” and causing a loud noise in the ear is avoided by an appropriately slower movement of the head restraint 3.

FIG. 5 and FIG. 6 show an arrangement of a head restraint on a vehicle seat corresponding essentially to the arrangement according to FIGS. 1 to 4, and so the same reference numbers are used here for functionally identical structural elements.

In contrast with the variant according to FIGS. 1 to 4, the drive device used in FIGS. 5 and 6 is a pneumatic drive 4′ which has a deployable airbag 32. The airbag 32 is connected to the frame 6 for holding the head restraint via a first securing device, comprising a fastening plate 29 on the frame 6 and a holder 30 which bears directly against the airbag 32 and is connected fixedly to the plate 29. At the other end the airbag 32 is connected to the impact plate 20 of the impact device 5 with a second securing device which essentially comprises a U-shaped holder 31.

In order to activate the pneumatic drive 4′, the airbag 32 is filled with air. It is contemplated for the airbag to be connected for this purpose to a general, already existing air supply in the vehicle. In order to make an even more rapid opening of the airbag 32 possible, it can also be driven in the manner known for airbags, via a pressure accumulator with an igniter.

With regard to its manner of operation, the pneumatic drive 4′ operates in the manner of the previously described drive device 4 with the spindle drive 9, with the embodiment according to FIGS. 5 and 6 being distinguished by a compact manner of construction and a simple design.

In all of the currently contemplated embodiments, it is particularly advantageous that they are reversible and can therefore be reused after being activated. With a reversible design of this type, the stipulations placed on the triggering reliability of the control electronics can be kept correspondingly less demanding because a possible erroneous triggering does not require the system to be completely replaced.

Of course, the arrangement according to the invention is not restricted to the structural embodiments shown here, because these can have numerous design variants. Thus, for example, instead of the described impact plate, the impact device may have an impact strap which is integrated with a correspondingly adapted securing device into the arrangement according to the invention.

In further contemplated embodiments, instead of the spindle drive and the pneumatic drive with an airbag, the drive device may also have other inflatable cushion elements or self-locking pneumatics with a cylinder or a hydraulic cylinder, as are well known in the prior art. 

1. A method for moving a head restraint of a vehicle seat in the event of a rear-end collision, the head restraint being moved in the forward direction of travel, characterized in that the movement of the head restraint (3) in the forward direction of travel (Y) takes place, firstly, by means of at least one driving device (4, 4′) and, secondly, is assisted by a movement of an upper body of an occupant located on the vehicle seat (1).
 2. The method as claimed in claim 1, characterized in that the movement of the head restraint (3) in the forward direction of travel by means of the drive device (4, 4′) takes place in terms of time before the displacement is assisted as a consequence of a rearward movement of the upper body of the vehicle occupant.
 3. An arrangement of a head restraint on a vehicle seat of a motor vehicle, in particular for carrying out a method as claimed in claim 1 or 2, characterized in that, in the event of a rear-end collision, the head restraint (3) can be moved in the forward direction of travel (Y) by means of a drive device (4, 4′) and an impact device (5) which absorbs a rearward movement of an upper body of an occupant located on the vehicle seat (1).
 4. The arrangement of a head restraint on a vehicle seat as claimed in claim 3, characterized in that the drive device (4, 4′) and the impact device (5) are arranged with respect to each other in such a manner that the impact device (5) assists a preceding movement of the head restraint (3) via the drive device (4) in the forward direction of travel.
 5. The arrangement of a head restraint on a vehicle seat as claimed in claim 3 or 4, characterized in that a frame (6) for holding the head restraint (3) can be pivoted by the drive device (4, 4′) in the forward direction of travel about an axis of rotation (15) fixed on the seat back.
 6. The arrangement of a head restraint on a vehicle seat as claimed in claim 5, characterized in that the frame (6) is guided in a guide (24) fixed on the seat back.
 7. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 3 to 6, characterized in that the impact device (5) is connected to the drive device (4, 4′).
 8. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 5 to 7, characterized in that an application of force to the impact device (5) causes the frame (6) for holding the head restraint (3) and the drive device (4, 4′) to additionally be pivoted through a further angle of rotation about the axis of rotation (15) fixed on the seat back.
 9. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 3 to 8, characterized in that the impact device (5) has an impact plate (20) or an impact strap provided to absorb a movement of the upper body of an occupant.
 10. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 5 to 9, characterized in that the impact device (5) is guided on a guide (24) fixed on the seat back, the frame (6) for holding the head restraint (3) and the impact device (5) preferably being guided on a common guide (24) fixed on the seat back.
 11. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 3 to 10, characterized in that the drive device (4) has at least one spindle drive (9).
 12. The arrangement of a head restraint on a vehicle seat as claimed in claim 11, characterized in that the spindle drive (9) has a spindle (10) which can be driven by a motor (11) in such a manner that a rotatable holder (12) which is connected to the frame (6) for holding the head restraint (3) and is intended for the spindle (10) is moved axially on the latter.
 13. The arrangement of a head restraint on a vehicle seat as claimed in claim 12, characterized in that the spindle (10) has a self-locking device.
 14. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 5 to 13, characterized in that the axis of rotation (15) runs through two pivots (16, 17) which are arranged symmetrically to each other, are fixed on the seat back and about which a respective spindle drive (9) can be pivoted.
 15. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 3 to 14, characterized in that the drive device (4) has at least one electric motor (11) and/or a pneumatic drive and/or a hydraulic drive.
 16. The arrangement as claimed in one of claims 1 to 10, characterized in that the drive device is designed as a pneumatic drive (4′).
 17. The arrangement as claimed in claim 16, characterized in that the pneumatic drive (4′) has an airbag (32) which can be deployed and which is connected to the frame (6) for holding the head restraint (3) via a first securing device (29, 30) and to the impact device (5) with a second securing device (31).
 18. The arrangement as claimed in claim 16 or 17, characterized in that the pneumatic drive (4′) is supplied with air via an air supply of the vehicle.
 19. The arrangement as claimed in claim 16 or 17, characterized in that the pneumatic drive (4′) can be driven via a pressure accumulator with an igniter.
 20. The arrangement of a head restraint on a vehicle seat as claimed in one of claims 3 to 19, characterized in that the arrangement is of reversible design. 